Abstract
Coral reefs are deteriorating worldwide prompting reef managers and stakeholders to increasingly explore new management tools. Following back-to-back bleaching in 2016/2017, multi-taxa coral nurseries were established in 2018 for the first time on the Great Barrier Reef (GBR) to aid reef maintenance and restoration at a "high-value" location-Opal Reef-frequented by the tourism industry. Various coral species (n = 11) were propagated within shallow water (ca. 4-7m) platforms installed across two sites characterised by differing environmental exposure-one adjacent to a deep-water channel (Blue Lagoon) and one that was relatively sheltered (RayBan). Growth rates of coral fragments placed onto nurseries were highly variable across taxa but generally higher at Blue Lagoon (2.1-10.8 cm2 month-1 over 12 months) compared to RayBan (0.6-6.6 cm2 month-1 over 9 months). Growth at Blue Lagoon was largely independent of season, except for Acropora tenuis and Acropora hyacinthus, where growth rates were 15-20% higher for December 2018-July 2019 ("warm season") compared to August-December 2018 ("cool season"). Survivorship across all 2,536 nursery fragments was ca. 80-100%, with some species exhibiting higher survivorship at Blue Lagoon (Acropora loripes, Porites cylindrica) and others at RayBan (A. hyacinthus, Montipora hispida). Parallel measurements of growth and survivorship were used to determine relative return-on-effort (RRE) scores as an integrated metric of "success" accounting for life history trade-offs, complementing the mutually exclusive assessment of growth or survivorship. RRE scores within sites (across species) were largely driven by growth, whereas RRE scores between sites were largely driven by survivorship. The initial nursery phase of coral propagation therefore appears useful to supplement coral material naturally available for stewardship of frequently visited Great Barrier Reef tourism (high-value) sites, but further assessment is needed to evaluate how well the growth rates and survival for nursery grown corals translate once material is outplanted.
Highlights
Deterioration in global coral reef health has prompted intensive efforts to explore and implement interventions that can enhance existing management efforts [1,2,3]
At Opal Reef we observed highly variable growth rates (ΔG; cm2 month-1) across coral taxa, determined from an entire year of growth at Blue Lagoon (BL) (August 2018-July 2019), with highest and lowest values observed for A. hyacinthus (10.8 ± 1.2, mean ± standard error) and M. hispida (1.0 ± 0.6) (Fig 2A; Table 2) (ANOVA p
Whilst it is clear that tackling climate change as the underlying cause of degradation to the Great Barrier Reef (GBR) is a priority [2, 11], our observations here suggest that nurseries benefit local “site stewardship” that collectively is central for improved regional-scale management strategies
Summary
Deterioration in global coral reef health has prompted intensive efforts to explore and implement interventions that can enhance existing management efforts [1,2,3]. Intervention approaches aimed at enhancing coral abundance have focused on general ecosystem recovery in response to physical disturbance, attempting to repair reef structural damage caused by ship groundings in Florida [4], and blast fishing or extreme weather/climate in the Indo-Pacific [8], and to restore populations of a particular species or genus, such as Acropora spp. decimated by disease throughout the Caribbean and western Atlantic [9, 10]. Until recently, such interventions had not been applied to the Great Barrier Reef (GBR). Many GBR “high-value reef sites”, in particular those generating high economic revenue via the tourism industry [12], face reduced coral abundance and rates of natural recovery [13]
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